This invention relates to single coil magnetic latching relays and, more particularly, to an arrangement for driving such a relay from an AC source.
When electronic circuitry is utilized to control the application of AC power to a load, a single coil magnetic latching relay is often utilized. The use of a relay provides isolation of the AC power from the electronic circuitry and also takes advantage of the higher current carrying capability of the relay contacts. An advantage of a single coil magnetic latching relay is that only a momentary pulse is needed to cause the relay to change state. Such a relay utilizes the remanent magnetic field of the armature to keep the relay in its driven state. Thus, a continuation of power to the relay coil is not required. However, some magnetic latching relays require a reversal of the polarity of current applied to the coil as well as a current reduction in order to release the relay from its energized state. This is because, if only a current polarity reversal were to be effected, the relay would again energize with an opposite polarity of the magnetic field in the relay armature. Utilizing DC power, the circuitry required to reverse polarity and at the same time reduce the current can be complex and expensive.
It is therefore a primary object of this invention to provide drive circuitry for controlling a single coil magnetic latching relay.
It is another object of this invention to provide such circuitry which is relatively simple in construction.
Since AC power is available, it is a further object of this invention to drive the relay from the AC source.